The Cardiac Cycle

Question 1

The cardiac cycle

Answer 1

All events that occur from the beginning of one heart beat to the beginning of the next

Question 2

What triggers a recurring cardiac cycle of A+V contractions and relaxations?

Answer 2

Orderly depolarisation and depolarisation sequence

Question 3

How long does diastole approximately take at 75bpm?

Answer 3

0.5s

Question 4

How long does systole approximately take at 75bpm?

Answer 4

0.3s

Question 5

Passive filling

Answer 5

Pressure close to 0 in A+V
AV valves open so venous return flows to ventricles
aortic pressure is at approx 80mmHg and Aortic valve is closed

Question 6

Events during cardiac cycle

Answer 6

• Passive filling
• Atrial contraction
• Isovolumetric ventricular contraction
• Ventricular ejection
• Isometric Ventricular relaxation

Question 7

Isovolumetric ventricular contraction

Answer 7

Starts after QRS, signalling ventricular depolarisation
ventricular pressure increases, eventually shutting AV valves- ‘lub’
Tension rises around close volume

Question 8

Ventricular ejection

Answer 8

Ventricular pressure> aortic/ PA pressure
Aortic and pulmonary valves open- silent
SV ejected by each ventricle
Aortic pressure rises
ventricles relax when pressure

Question 9

Isovolumetric Ventricular Relaxation

Answer 9

A+P valves close, tension around closed volume (ventricle) falls
AV valves open when ventricular pressure

Question 10

What causes S1/ lub sound?

Answer 10

mitral and tricuspid valves closing, signalling start of systole

Question 11

What causes S2/ dub sound?

Answer 11

Aortic and pulmonary valves closing, signalling beginning of diastole

Question 12

When does Jugular Venous Pulse arise?

Answer 12

Immediately after right atrial pressure waves, which is an indirect measurement of central venous pressure